In the study, a nonlinear joint element is implemented in a finite element computer program and it is used to model the opening and closing of contraction joints in concrete arch dams. The joint element is combined with shell, solid and fluid finite elements to model a complete arch dam system. Special consideration is given to resolving the stress distribution near the joints by using a refined mesh of solid elements. A numerical procedure for solving the equations of motion recognizes that the nonlinearity in the model is restricted to the joints. The monoliths between contraction joint elements are modeled as linear substructures: this provides a significant reduction of computation in the iterative solution of the nonlinear equations of motion. A study of the finite element modeling shows that the joint opening mechanism reduces the effective vibration frequency of a structure and demonstrates the same qualitative trends observed in the experimental testing of an arch rib. The results of an earthquake analysis of a typical concrete arch dam indicate the expected release of arch tension stresses and subsequent redistribution of forces. The computer program ADAP-88 implements the nonlinear joint element and solution procedure along with shell, solid, and fluid elements for modeling an arch dam system. The program includes a finite element mesh generator.